Yes, OOTP 2006 is the next step up from OOTP 6.
It was previously named OOTP 7, but they changed the name.
However, OOTP 2006 is a complete rewrite - no lines of code from V6 were carried over. This also means that certain features that were in OOTP 6 have no made the cut from OOTP 2006.
The interface is completely different, and the focus of the game is different as well. OOTP 2006 is now a "global" simulator, where you can add international leagues wherever you want. However, adding this functionality seems to have taken away from other parts of the game, including AI strength and basic functionality.
Personally, I prefer 6.5 and many others do as well, but it is up to you.
OOTP 2006 Vs OOTP 6.5:
http://www.ootpdevelopments.com/boar...d.php?t=123790